An ECB spokeswoman told us that all the people affected had been contacted, but stressed that it was not known whether all 20,000 people on the database were affected.

She said that as far as the bank knows, the information has not yet been dumped online. This suggests the attack was carried out purely for financial gain, as hackers often like to show off the results of their work by publishing their haul online.

The bank said it first discovered the theft when it received an anonymous email asking for cash in exchange for the data cache. It stressed no "market sensitive data" was compromised and said "data security experts have addressed the vulnerability".

No critical systems were accessed, the bank claimed, and the hacked site was linked to its public database, which is separate from any internal system.

German police have now begun an investigation and all passwords on the system have been changed as a precaution.

Did you receive a letter or email from the ECB? Was your data compromised? Get in touch and let us know. ®